1. Field of the Invention
The present invention relates to an alternator driven by an internal combustion engine, for example, and in particular, relates to a stator construction for an automotive alternator mounted to an automotive vehicle such as a passenger car or a truck.
2. Description of the Related Art
FIG. 34 is a perspective showing an example of a stator of a conventional automotive alternator. In the figure, the stator 108 includes a cylindrical stator core 136 having a number of slots 136, and stator winding groups 135 arranged inside the slots 136a. Furthermore, the stator core 136 has a weld portion 136b at one circumferential position.
Next, a method for manufacturing the stator 108 will be explained. First, the belt-shaped bodies 120 shown in FIG. 35 are punched into a comb-shape and cut off at a predetermined length. Thereafter, the cutoff belt-shaped bodies 120 are laminated to form a parallelepiped laminated body 150, as shown in FIG. 36. Belt-shaped bodies 120 having a width of 12 mm and a thickness of 1 mm, for example, are used, all the bodies having the same thickness. Then, the laminated body 150 is formed into a parallelepiped having dimensions of 12 mmxc3x97336 mmxc3x9727 mm, for example.
At the same time, the stator winding groups 135 are first formed into an overall flat shape such that the coils can be inserted without modification into every third slot 136a in FIG. 36, and are then inserted into the slots 136a as shown in FIG. 37. Thereafter, the laminated body 150 is bent into a cylindrical shape by means of a shaping device (not shown) to form the stator core 136. After the bending process, both ends of the laminated body 150 are joined together by welding at the weld portion 136b in FIG. 36.
By being rolled into the cylindrical shape, the stator core 136 prepared in this way can be provided with a number of slots 136a opening towards a center, and with teeth 136c defining each slot 136a. There are thirty-six slots 136a and thirty-six teeth 136c per phase per pole (3 phasesxc3x9712 poles).
In this sort of method for manufacturing the stator 108, when inserting the stator winding groups into the slots 136a, the stator winding groups may be moved in one direction so that the stator winding groups 135 can be arranged easily and with a high density, and excessive force and bending are not applied, thereby preventing damage to the conductors. Furthermore, since there is no need to form the stator winding groups 135 into a cylindrical shape in advance, the manufacturing of the stator winding groups 135 is facilitated, and in addition, there is no longer any need to adapt cylindrical winding groups to fit into a cylindrical stator core, thereby improving the manufacturing efficiency of the stator.
In the stator of the conventional automotive alternator constructed in this manner, because the stator core 136 can be obtained by bending the parallelepiped laminated body 150 into the cylindrical shape, there has been a problem of the stator core 136 becoming a circular tube which is undulates axially around its entire circumference as shown in FIGS. 38 and 39. Since there are no obstructions outside the laminated body in the circumferential direction, corrections can be made by means of the shaping device when the cylindrical shape is formed, but because the coil ends of the inserted winding groups project around the entire circumference at both axial ends, it has been difficult to correct the laminated body portions.
Furthermore, because the slots 136a and the teeth 136c are formed alternately, that is to say with protrusions and recesses, on an inner circumferential side, there is alternately high and low rigidity in the circumferential direction, and because this type of laminated body is bent into a cylindrical shape, there has also been a problem of deterioration in the shape of slots 136a and teeth 136c. An additional problem has been that warping and undulating has occurred in the core-back portions at the spine portions of the slots 136a, making quality unstable, etc.
The present invention aims to solve the above problems and an object of the present invention is to provide an automotive alternator in which warping and undulating of the stator core can be reduced and quality can be stabilized at low cost.
In order to achieve the above object, according to one aspect of the present invention, there is provided an automotive alternator including:
a rotor;
a stator disposed facing an outer circumference of the rotor; and
a bracket for supporting the rotor and the stator,
the automotive alternator further including:
a stator core including a laminated core formed circumferentially with a number of slots extending axially; and
a polyphase stator winding installed in the slots at a predetermined slot pitch,
the laminated core being formed into an annular shape by:
forming a main laminated body by laminating a number of main lamination plates formed with a number of teeth defining the slots on one side of a yoke;
forming a laminated body by laminating an end plate having higher rigidity than the main lamination plates onto at least one end surface of the main laminated body in a direction of lamination;
disposing the polyphase stator winding in the slots; and
placing end portions of the laminated body in contact with each other by bending the laminated body such that opening portions of the slots are on an inner circumferential side.
The laminated body may also be rectilinear in shape prior to bending.
The polyphase stator winding may also include a number of winding sub-portions in each of which a long strand of wire is wound so as to alternately occupy an inner layer and an outer layer in a slot depth direction within the slots at intervals of a predetermined number of slots, the strands of wire folding back outside the slots at axial end surfaces of the stator core to form turn portions; and the turn portions of the strands of wire may also align in a circumferential direction to constitute coil end groups.
The rotor may also include a rotor winding for generating magnetic flux on passage of an electric current and a rotor core covering the rotor winding, a number of claw-shaped magnetic poles being formed in the rotor core by the magnetic flux; and
the number of slots in the stator core may also be two or more per phase per pole.
2n strands of the strands of wire may also be disposed in a row in a slot depth direction in each of the slots and the turn portions of the strands of wire arranged so as to align into n rows in a circumferential direction.
2n strands of the strands of wire may also be disposed in a row in a slot depth direction in each of the slots and the turn portions of the strands of wire arranged so as to stack up into n layers.
Interlocking portions may also be disposed in at least the end plate and the main laminated plates facing the end plate so as to connect both together.
The laminated plates and the end plate may also be integrated by being welded together in the direction of lamination at a rear surface portion of the teeth being a surface on the opposite side from the teeth.
Rigidity of the end plate may also be made greater than the main lamination plates by making a thickness of the end plate greater than the main lamination plates.
Rigidity of the end plate may also be made greater than the main laminated plates by providing ribs.
The ribs may also be formed in at least a circumferential direction of the stator.